This invention relates in general to the waste water outlet of sanitary plants comprising a siphon forming a water seal to which is connected a waste pipe for connection with sewers. As it is well known that a permanent water seal in the form of siphons used in sanitary equipment is one of the basic requirements for the normal operation of a waste water outlet plant.
In a waste outlet system, siphons undergo several influences the consequences of which may be flowing of water from the apparatus itself by negative pressure in the connecting line or sucking caused by flowing water coming from other devices.